About your grandfather (may he rest in peace), sadly, he would have died eventually, no matter what. I’m sorry for all of the lost years that you could have spent with him, but think about what could have happend if you were older, and more attached to him when he passed. It would have been worse to see him go then, than to have only known him for seven years. I know it might not make much sense to you, but losing him early was better.
Besides, if he was a God-loving man (sorry if he wasn’t) and you choose to be one too, you could reunite with him in Heaven.

I don’t know if I changed your mind about God, but if there is anyway I could tell me.